Rotary fuel metering pump and emergency means insuring fuel feed upon pump failure



4 m l R. w, a m w W m m 5 P I V N w H UH h\\ k m 2 e r MN NW A 3 J% QQ m J. A. BOLT ET AL ETERING PUMP AND EMERGENCY MEANS INSURING FUEL FEED UPON PUMP FAILURE Nov. 28, 1950 ROTARY FUEL M Filed April 6, 194a 1950 J. A. BOLT ET AL 2,531,564

ROTARY FUEL METERING PUMP AND EMERGENCY MEANS INSURING FUEL FEED UPON PUMP FAILURE Filed April s, 1946 a Sheets-Sheet 2 22 TIPS. 5

A T'TOP/VE) Patented Nov. 28, 1950 ROTARY FUEL METERING PUMP AND EMERGENCY MEANS ENSURING FUEL FEED UPON PUMP FAILURE Jay A. Bolt, South Bend, Ind., and Frederick P. Jackson, Dayton, Ohio, assignora to Bendix Aviation Corporation, South Bend, Ind., a cornotation of Delaware Application April s, 1946, Serial No. 860,248

13 Claims. 1

This invention relates to fuel metering systems, and it is primarily concerned with metering systems or devices of that type wherein fuel is supplied to a power plant or engine under pressure and is measured or metered on the basis of engine speed, usually modified by one or more op: erating functions or characteristics indicative of mass air flow to the engine. or air consumption. Such a device utilizes an engine-driven pump which delivers fuel under pressure to a fuel-inlet poppet valve controlled by a speed-responsive element such as a centrifugal governor rotating in synchronism with the engine and whose thrust is opposed by a. metering head diaphragm. Metered fuel may be delivered through a discharge nozzle adapted to open when the metered fuel pressure attains a predetermined value, for example, pounds per square inch. To obtain a compact unit, it has become common practice to utilize an inbuilt fuel pump, the pumping elements being mounted on a drive shaft or rotor in alignment with the centrifugal governor and having a drive connection with the latter.

In metering systems of this type, should the pumping elements of the engine-driven pump which delivers fuel under pressure to the gov ernor-controlled valve seize or otherwise be rendered ineffective, the pressure in the system may be reduced to a point where the delivery of fuel to the engine will stop, and if a constant pressure fuel delivery nozzle is utilized, the fuel feed will stop entirely should the pressure drop below nozzle discharge pressure. Also in installations where the engine-driven pump drives the poppet valve governor, failure of the pump will likewise result in failure of the governor function. Again, in cases of aircraft engines or power plants utilizing an independently-controlled boost pump in series with the main engine-driven fuel pump, should the engine fail as for example during takeoff, the engine-driven pump will stop, and since the latter pump may not pass sufficient fuel to overcome nozzle discharge pressure, or to permit proper functioning of the metering system, the supply of fuel to the engine is immediately cut off even though the pilot may operate the boost pump.

The primary object of the present invention, therefore, is to provide a fuel metering system of the type specified wherein should the enginedriven fuel pump fail, metering of fuel to the engine may be maintainedirrespective of such failure.

Another object is to' provide a safety or emer gency system for fuel metering devices of the rotary pump type which, should the engine-,

driven fuel pump fail, permits the metering systern to function through operation of a boost pump or other pressurizing device controlled either automatically or by the pilot or operator.

A further object is to provide a fuel metering device of the rotary pump type particularly adapted for aircraft engines incorporating an emergency fuel supply and metering system which requires a minimum number of parts in addition to those already present and therefore involves only a small additional cost and little or no additional weight, and which at the same time is capable of operating over long periods of time without danger of failure and with a minimum of wear on the moving parts.

The foregoing and other objects and advantages will become apparent in view of the followsection of the engine-driven fuel pump assembly;

Figures 5 and 6 are sections taken on the lines 5-5 and 66, Figure 4; and

Figure 7 is a detail view of the pump rotor.

Referring to the drawings in detail, the metering device comprises a main housing I0 having a portion shaped to define a fuel pump intake chamber H to which fuel may be supplied from a fuel tank I2 through conduit IS. A fuel pump is generally indicated at M, and as here shown, is of the vane type comprising a rotor l5 (see Figures 4 to 7, inclusive) formed with a center bore mounting a hollow eccentric sleeve orcylinder l6, and a series of radial slots mounting pumping elements or vanes IT. The rotor is supported for rotationin a sleeve or cage 18 formed with intake and exhaust openings at an inter-- mediate point and terminating at its opposite ends in annular portions l8, l8" which cam the blades radially inwardly against the sleeve or cylinder [6.

The rotor I5 is mounted on a shaft is having a reduced center portion l9 which projects through the cylinder l6 and terminates at its left hand end in an enlargement IS". The righthand end of the rotor as viewed in Figure 4 is reduced in diameter as indicated at 20, and the shaft i9 is formed with a transverse bore 2| adapfii! receive a shear pin 22 which projects into a registering bore formed in the reduced end 20 of the rotor and provides a driving connection between the shaft and rotor.

The pump takes fuel from the chamber I I and forces it under pressure into chamber 23 (see Figures 1, 2 and 3) defined in part, by a wall 24 having a transverse portion 24 shown as formed integral with the housing I0, said wall 24 and housing l having portions 25 and 26 which are contoured to receive the rotor cage l8. The

. chamber 23 may be aptly termed the governor chamber. A screw 21 projects into a spline or keyway formed in the cage [8 and maintains the latter against displacement.

End caps 28 and 29, the latter being removably secured to the housing l0, support the sealing and bearing assemblies for the outer end of shaft H, to which oil may be supplied through duct 30 forming part of the engine oiling system. A drive pinion or gear 3| is keyed on the outer end of shaft I9 and forms part of a drive connection between the pump and the engine.

The left end of the rotor I is reduced as at 32 and is journaled in a bushing or bearing 33, the latter in turn being mounted in bosses 34, 34' formed integral with the housing or casting Ill, compare Figure 4 with Figures 1 and 3. The left end of the rotor shaft is projected outwardly and has keyed or otherwise secured thereon a bushing 35 which forms the hub portion of a cup 36 having a driving connection with a governor and poppet-valve assembly comprising an elongated valve member 31 formed with a reduced stem 31. The valve member 31 is mounted to slide in a bushing 38 having an attaching flange 38' at its outer or left-hand end secured to the adjacent wall of the unmetered fuel chamber C, to be described, said bushing being formed with a valve seat defining a valve port 40. The reduced portion of the valve stem 31' is encircled by a spring 4| which at its left end abuts a shoulder formed on the valve stem and at its opposite end bears against the inner race of a thrust bearing 42 held in adjusted position by end nut 43.

The governor weights are indicated at 45; they are secured on pins 46 and have formed integrally therewith fingers 45' adapted to engage the thrust bearing 42 and urge the poppet valve 31 toward open position with a force depending on the speed of rotation and the resultant centrifugal effect of the weights 45. The pins 46 are anchored in yokes 41 forming part of a hub member 48 carrying the outer race of a bearing assembly 49, the inner race of the bearing assembly being secured on the bushing 38. A driving connec tion between the rotor shaft 19 and governor is provided by means of lugs 5| projecting radially from the flange of the hub 48 and engaging in open slots formed in the edge of the cup 36, the latter serving to reduce turbulence of fuel in the governor chamber and to also limit the throw of the governor weights under certain conditions, as when there is no appreciable differential pressure across the metering head diaphragm, indicated at 52.

The diaphragm 52 is clamped between the radial portions or flanges of bushings 53 and 54. Bushing 53 is slidingly mounted in a guide sleeve 55, while bushing 54 has connected thereto a stem 56. A cable 51 connects at one end with the stem 56 and at its opposite end with the poppet valve 31. To stiffen the cable sufficiently to prevent buckling due to idle spring thrust, a light wire spring 51' encircles the cable. An idle spring 58 engages the outer side of the diaphragm bushing 54 and applies predetermined pressure in an opening direction on the poppet valve 31 at low idling speeds to ensure sufllcient metering head pressure for idling purposes.

The pump-intake or low pressure chamber II is separated from the governor or pump-delivery chamber 23 above the latter by the transverse portion 24' of the wall 24 mounting a two-way bypass valve assembly generally indicated at 60 and comprising a valve cage 6| which is threaded in a bore formed in said wall and has a seat 6| at its upper edge and passages 62 in the base thereof. A guide pin 63 projects upwardly from said base. A valve member 64 has a counterbored central portion telescoped on or slidlngly engaging tne upper free end of said pin and an outer valve element 64' adapted to engage the seat 6|. The valve member 64 is carried by a diaphragm 65 of substantially the same mean effective area as the seat 6|, said diaphragm forming a movable or flexible wall of a balancing chamber 66. A spring 61 urges valve member 64 onto its seat and allow it to open when the pressure in chamber 23 exceeds the pressure in chamber 66 by some predetermined amount, dependent upon the strength of spring 61.

Means are also provided whereby should the pressure in the governor chamber 23 drop below a certain value, due for example, to failure of the engine-driven pump l4, fuel will pass from the low-pressure side (chamber ll) of said pump into said chamber 23. To afford compactness and lower costs of manufacture, a return bypass has been built into the valve assembly 60. Thus the valve member 64 is formed with a series of radial inlet openings 68 which feed into an annular passage or valve port 68 surrounding the central portion of said member, said port being normally closed by a valve member 69 urged to its seat by a spring 16 plus the pressure existing in chamber 23. As long as the enginedriven pump i4 operates normally, the pressure in chamber 23 is sufficient to maintain the valve 69 seated, and the by-pass valve 60 can then act in one direction only, viz. to relieve excess pressure from chamber 23, but should the pressure in chamber 23 drop below a predetermined value, valve 69 will open and permit fuel to flow from chamber H into chamber 23.

In order to provide a substantially constant pressure drop across the valve 31 and balance the various pressures in the metering system, the chamber 66 is connected by a, duct or passage 1|, II with chamber C and which may be considered the unmetered fuel chamber. Chamber 66 also communicates with chamber ll through a restricted orifice or bleed 12 to permit complete filling of. chamber 66 and relieve excess pressure developed in said latter chamber by engine heat when the engine is stopped.

When the pump is initially placed in operation and suilicient pressure is built up in the chamber 23, the valve 64 will open. When this valve opens, fuel pressure will build up in the chamber II to a predetermined value, whereupon fuel will pass through orifice 12 into chamber 68. Since this latter chamber is in communication with the unmetered fuel chamber C, the pressure on the top side of diaphragm 65 will be unmetered fuel pressure while that on the lower side of the valve 64 will be equivalent to that in the governor chamber 23; and the differential between these chambers 65 and 23, and hence the drop across the valve 31 will be maintained accuses at a substantially constant predetermined value as determined by the spring 01 irrespective of the flow of fuel delivered by the unit.

The valve generally indicated at II, Figure 1. is an idle cut of! valve; it is used to completely cut of! fuel to the engine to stop the latter. This valve is provided with a stem 19 and a lever 11. The valve has a cylindrical rotary valve member 19 located in the fuel discharge conduit I9 and having a through passageway or valve port adapted to register with said conduit when the valve handle is turned to "on" position. In the position shown. the valve is open and fuel may flow through the conduit I9. The fuel discharge conduit is adapted for attachment of a suitable fuel line 19' leading in the present instance to a spray nozzle, to be described, but which may lead to any other suitable discharge device, depending upon what type of power unit is being supplied with fuel.

It will be noted that the passage or duct II connects with the continuation II thereof through a valve port in the form of a through bore ll formed in a cylindrical rotary valve member II mounted on and rotatable with valve stem 16. Thus when the idle cut off valve I5 is closed, valve 9| is likewise closed and communication between the unmetered fuel chamber 0 and the chamber 60 is broken. The reason for this is that should the unmetered fuel pressure still be applied to chamber 69 after fuel flow is stopped and during further running of the engine due to-momentum, the by-pa'ss valve 94 would not open and dangerously high pressures in the system would result.

It is important that vapor be completely eliminated from the pressure chamber in which the governor and poppet valve assembly operate.

Since fuel in vapor form islighter than when in the liquid phase, it tends to gather in the governor chamber, due. to the fact that the heavier liquid fuel is thrown outwardly by centrifugal force, where the lighter vapor reduces the specific gravity of the fuel which in turn tends to reduce the fluid resistance to movement of the governor weights and increases the tendency of the vapor to centrifuge or move towards the central area of the governor chamber. Such asystem is disclosed in copending application Serial No. 586,224 filed April 2, 1945. in the names of Willard F. Blakeway and Albert P. Schnaible, and assigned to the assignee of the instant invention. A unique feature of this vapor elimination system is that it acts to centrifuge air and vapor from the fuel before any of the fuel in the delivery chamber 23 is passed through the relief valve back to the low pressure side of the engine-drivenpump, so that it is less likely to completely vaporlock the pump, even though the system may be operated without boost pump or tank pressurization when cruising at altitude.

The spinning cup which houses the governor weights is formed with a series of holes or openlugs 09 in the peripheral and end walls thereof. and the hub member is also preferably formed with a series of similar openings 86', the lighter fuel components passing into thecentral area of 6 the spinning cup through these holes 99, 96'. From this point the vapor may pass by way of a port or passageway 91 formed in the left extremity of the rotor shaft and thence by way of discharge passages 89,99 to an annular collecting chamber 99 formed in the boss 34. A vapor vent channel communicates the annular chamber 99 with a vapor vent chamber 9|, the latter being provided with a float 92 carrying a valve member 93 slidable on the lower end of a hollow depending stem provided with a port 94, said valve 93 controlling a vapor discharge passage 90 which may lead to the fuel tank or to some other suitable point such as the engine air intake. An apertured inverted cup-dike member 96 provides a smooth internal wall to permit free vertical movement of the float. During periods of operation, a continuous flow of liquid and/or vapor occurs from the center portion of the governor chamber to the float chamber 9|. In the absence of vapor, the liquid fuel in chamber 9I fllls the latter and the float valve 93 closes the port 90. Fuel thereafter supplied to chamber 9| escapes through a passage 91 and restriction as to the by-pass chamber II. Any vapor centrifuged towards the center of the spinning cup escapes through the passages 81, 90 to the annular chamber 89 and thence through the channel 90 to the float chamber 9|. When there is littleor no vapor or air in the float chamber 9I, the valve port 99 is closed by the valve 99; but when vapor or air enters said chamber, it depresses the liquid fuel level, the float drops and the valve 93 uncovers the port 94, permitting vapor and air to escape back to the fuel tank through conduit or passage 95. As the vapor escapes, liquid fuel entering chamber 9| raises the fuel level therein and moves the float 92 upwardly to close port 94.

The fuel in chamber C may pass through a metering orifice I00 into metered fuel chamber B, Figure 1, which is in communication with the discharge conduit 19. The orifice I00 is controlled by a needle I0l connected to and regulated by a capsule or bellows I02 mounted in a housing I02, a pipe connection I03 communicating manifold pressure to said housing. As manifold pressure increases, bellows or capsule I02 is compressed, thereby retracting needle I 0I from metering orifice I00, and as manifold pressure decreases bellows I02 expands, thereby projecting needle IOI into the said metering orifice. The bellows I02 is connected at its rear end to the movable end of a bellows I04, the interior of which is vented to the atmosphere at I05 and whereby the action ofv the manifold pressure capsule is modified by changes in atmospheric pressure and which is an index of exhaust back pressure. Unmetered fuel may also flow through a passage I05 and thence through supplemental metering orifice I01 into the metered fuel chamber B, the orifice I01 being controlled by a needle I08 connected to a temperature-responsive bellows I09 which in turn is operatively connected to a temperature-sensitive element mounted in the engine intake manifold or other point indicative of the temperature of the air flowing to the engine cylinders.

A fuel discharge nozzle is generally indicated at I I0: it receives metered fuel under pressure from the conduit 19 and is adapted to open at some predetermined pressure, for example 10 pounds per square inch, and discharge fuel into an air-induction conduit I I I for supplying air to the engine, not shown. The nozzle II 0 may be provided with a diaphragm chamber vented to nozzle.

The fuel tank I2 has mounted in the base thereof a boost pump 6, preferably of the submerged positive-displacement or vane type, the pump being herein shown as electrically driven and controlled by a switch I" mounted in convenient reach of a pilot or operator and connecting with the pump through line wire III. A source of potential such as a battery is indicated at II9.

The high pressure or discharge side of the pump H8 is connected to the conduit H: by conduit I20, and a check valve iZI permits fuel to bypass the pump H6 when the latter is idle, and also checks back-flow of fuel into the tank when the said pump is in operation and pressurizing fuel in conduit 53. A relief valve I22 determines the maximum pressure delivery of the pump '8, said valve being connected to a diaphragm I23 forming the movable wall of a chamber I24 in which a spring I25 is mounted and adapted to engage the diaphragm I23. The chamber I24 is vented to the unmetered fuel chamber C of the regulator by means of a conduit [26. The spring 525 may have a force equivalent to the drop across the poppet valve 31, for example between five and ten pounds per square inch, so that the effective pressure of the pump l6 will be sufllcient to ensure ample fuel flow under all conditions of operation.

A pressure gauge 52? is provided in the pilots compartment or other point within view of an operator, and communicates with the governor chamber 23 through pipe or conduit 628. Should the pressure in chamber 23 drop below some safe value, due to failure or faulty delivery of the engine-driven pump i i, the pilot will be immediately notified and turn on the boost pump Hi.

The operation is as follows:

The fuel pump it may be suitably geared to the engine or power plant to be supplied with fuel and driven thereby. Rotation of the rotor shaft 59 causes the drive to be applied to the pump rotor through the shear pin 22. As the rotor rotates, fuel is drawn in through the conduit I3 from the tank 42 and into the chamber H, from which it is forced by the rotor blades or vanes into the governor chamber 23. The relief valve 66 is set to maintain the fuel in chamber 23 at a predetermined pressure over and above the pressure in unmetered fuel chamber 6, and when this pressure is exceeded, the valve M is opened and the excess fuel is lay-passed back to the chamber ii. When the engine is operating, the rotating governor weights Q and the idle spring 58 tend to open the valve 3? and permit fuel under pressure to pass from the chamber 23 through the valve port it into the unmetered fuel chamber C. The fuel flows through metering orifice i053 into the metered fuel chamber B and thence through the fuel conduit 79 to the fuel discharge nozzle iii As soon as the metered fuel pressure attains a value equivalent to the pressure setting of the discharge nozzle, the latter opens and fuel is discharged into the engine intake conduit or other point of supply. The valve 31 will float towards open or closed position until the governor head acting on diaphragm 52 balances the force of the governor weights 45. Since the governor rotates in direct relation to engine speed, the thrust of the governor weights is proportional to speed squared and therefore the balancing differential across the diaphragm l! is maintained proportional to speed squared and the metering head across the metering orifice IIIII is also maintained proportional to speed squared for any given position of the needle III. Assuming a fixed area of the metering orifice IIIII, then flow therethrough is proportional to the square root of the pressure difference thereacross and hence is proportional to engine speed. For a constant condition of manifold pressure and exhaust back pressure, the air flow to the engine will vary in direct proportion to engine speed, and the control mechanism will correspondingly vary the quantity of fuel supplied to the engine. Since the mass rate of air flow to the engine is dependent not only on the engine speed but also upon manifold or charging pressure, air temperature and exhaust back pressure, the area of orifice I00 is controlled by needle IIII while the area of orifice I01 is controlled by the temperature responsive needle Ill. Thus as the manifold pressure is varied, as by actuation of a throttle valve in the air intake conduit, or by variation in speed of a supercharger at a'given throttle opening, such variations will be transferred to the chamber defined by the housing 502 and imposed on the capsule therein, the effective action of the capsule being modified b changes in atmospheric pressure through the action of bellows I04, and compensation for changes in temperature being had through control of orifice In! by temperature needle I".

Should the rotor of the engine-driven vane pump l4 jam or encounter an obstacle or due to some other cause be subjected to torsional stress such as will effect shearing of the pin 22, the rotor will stop (but not the governor) and the pressure in governor chamber 23 will immediately drop, such drop being visually indicated on the gauge 21 which is constantly being read by the pilot or operator. The pilot may then immediately turn on the switch H1 and start the boost pump H6, thereby building up the pressure in the chamber 8! to a point where the valve 59 opens and permits fuel to pass from the chamber II into the governor chamber 23, the pressure in chamber 23 now being determined by the setting of the spring I25 for the valve I22. Since the pump H6 is controlled independently of the engine, it will replace the engine-driven pump M, or provide a substitute for the latter, while at the same time the drive on the governor continues through the rotor shaft I8 and cup 36. Thus normal metering will be had irrespective of failure of the pump i4.

Usually, out of precaution, the pilot turns on the boost pump during take-off until the aircraft attains a safe height, such precaution being taken to ensure ample reserve pressure in the fuel system in case the engine should stop momentarily or falter and thereby stop the drive on the engine-driven fuel pump. With the present improved safety device, not only will such action ensure a supply of fuel to the priming system but there will also be full pump pressure on the fuel in the governor chamber in case the pressure in said latter chamber should drop as a result of faulty engine operation, or due to pump failure caused by jamming or seizing of the rotary pump element.

Actual tests show that the eiilciency of the 9 metering system is substantially unaffected by change-over from theengine-driven pump to the boost pump, and also that the emergency system may be. operated for long periods of time without material wear and resultant danger of failure of running parts.

It will be understood that no attempt has been made herein to set forth all of the advantages and operating characteristics of the invention, and that the drawings are simply illustrative and that in actual practice it is usually necessary to make certain rearrangements and changes in parts to adapt the inventionto differentinstallations, the scope of the invention being limited only by the appended claims.

We claims 1. In a system for metering fuel to an engine wherein the flow of fuel through a conduit to the engine is regulated by a valve located in the conduit and controlled by an element rotating in synchronism with the engine and to which fuel is supplied through the conduit under pressure by an engine-driven pump provided with a rotor and having a drivingconnection with said element; means whereby should the rotor of the engine-driven pump fail due to jamming or seizure the drive on said rotating element is maintained, and means supplementing said pump for maintaining asupply of fuel under pressure to said valve.

2. In a system for metering fuel to an engine wherein the flow of fuel through a conduit to the engine is regulated by a valve located in the conduit and controlled by an element rotating in synchronism with the engine and to which fuel is supplied under pressure by an engine-driven pump provided with a rotor and having a driving connection with said element; means whereby should the rotor of the engine-driven pump fail due to jamming or seizure the drive on said rotating element is maintained, and means selectively operable independently of the engine for maintaining a supply of fuel under pressure to said valve.

3. In a system for metering fuel to an engine wherein the flow of fuel through a conduit to.

the engine is regulated by a valve located in the conduit and controlled by a governor having a drive connection with the engine through an engine-driven fuel pump provided with a pumping element and a driving member therefor; means whereby should the pumping element of the engine-driven pump jam or seize the drive on the governor is maintained through said driving member, and means operable independently of the engine-driven pump for pressurizing the fuel in said conduit upstream of said valve.

4. In a system for metering fuel to an engine wherein the flow of fuel through a conduit to the engine is regulated by a valve located in the conduit and controlled by a governor having a drive connection with the engine through an engine-driven fuel pump provided with a pumping termined value relatively to the pressure downstream thereof. 5. In a system for metering fuel to an engine wherein the flow of fuel through a conduit to the engine is regulated by a valve located in the conduit and controlled by a governor having a drive connection with the engine through an engine-driven fuel pump provided with a pumping element and a driving member therefor;

6. In a system for metering, fuel to an engine wherein the flow of fuel through aconduit to the engine is regulated by a valve located in the conduit and controlledby a governor having a drive connection with the engine through an engine-driven fuel pump provided with a pumping element and a driving member therefor; means whereby should the pumping element of the engine-driven pump jam or seize the drive on the governor is maintained through said driving member, means defining a low pressure intake chamber on the upstreamside of said engine-driven fuel pump and a high pressure delivery chamber on the downstream side thereof in communication with said valve, an independently controlled boost pump arranged to pressurize fuel into said intake chamber, and a reverse flow by-pass valve assembly between said chambers, said by-pass valve assembly operating to by-pass fuel from the delivery to the intake chamber under normal periods of operation and to by-pass fuel from the intake to the delivery chamber under emergency periods of operation.

7. For use in a fuel metering system foi'iengines, a fuel metering device including-a valve, a governor rotatable in relation to engine speed connected to said valve for controlling the latter, a fuel pump having a pumping element and a drive member therefor adapted to be driven by the engine, means providing a drive connection between the drive member. and said governor, and means whereby should the pumping element jam or seize thedrive on the governor will be maintained..

8. For use in a fuel metering system for an engine, a fuel metering'device having a fuel valve and a governor connected thereto for controlling the valve, a fuel pump adapted to be driven by the engine, said fuel pump including a drive shaft carrying a rotatable pumping element, means providing a driving connection between said shaft and said governor, and means providinga drive connection between said shaft and said pumping element,said latter means being, adapted to automatically disconnect the pumping element from the'shaft when the. torque stress on therotatable pumping element exceeds a predetermined valve. r

9. In a system for metering fuel to an engin'e wherein the flow of fuel through a conduit to the engine is regulated by a valve located in the conduit and controlled by an element rotating in synchronism with the engine and to which fuel is supplied under pressure by an engine-driven pump provided with a pumping element and a driving membertherefor having a drive connec;

tion with both of said elements. means whemify should the pumping element of the engine-driven pump jam or seize the drive on said rotating element is maintained, means defining a low pressure intake chamber upstream of said enginedriven pump and a high pressure delivery chamber downstream thereof in communication with said valve, a boost pump operable independently of the engine-driven pump arranged to pressurize fuel into said intake chamber in the event of failure of said engine-driven pump, means for lay-passing fuel from said intake chamber around said engine-driven pump to the delivery chamber when the pressures in said chambers attain predetermined relative values, and a spring-biased relief valve for said boost pump having a pressure-responsive control element vented to a source of reference pressure changing with changes in pressure in the fuel metering system. 1

10. In a system for metering fuel to an engine wherein the flow of fuel through a conduit to the engine is regulated by a valve located in said conduit and controlled by an element rotating in synchronism with the engine and to which fuel is supplied under pressure by an enginedriven pump provided with a pumping element and a driving member therefor having a drive connection with both of said elements, means whereby should the pumping element of the engine-driven pump jam or seize the drive on said rotating element is maintained, means defining a low pressure intake chamber on the upstream side of said engine-driven pump and a high pressure delivery chamber on the downstream side thereof in communication with said fuel valve, an independently controllable boost pump arranged to pressurize fuel into said intake chamber, a by-pass valve adapted to bypass fuel from the intake chamber to the delivery chamber around said engine-driven pump when the pressures in said chambers attain predetermined relative valves, a relief valve for said boost pump having a pressure-responsive control element vented to the fuel pressure downstream of said fuel valve, and a spring augmenting the pressure of the fuel on said latter element having a spring force substantially equal tothe pressure drop across said fuel valve.

11. In a system for metering fuel to an engine wherein the flow of fuel through a conduit to the engine is regulated by a valve located in said conduit and controlled by an element rotating in synchronism with the engine and to which fuel is supplied under pressure by an enginedriven pump provided with a pumping element and a driving member therefor having a drive connection with both of said elements, means whereby should the pumping element of the engine-driven pump jam or seize the drive on said rotating element is maintained, means defining a low pressure intake chamber on the upstream side of said engine-driven pump and a high pressure delivery chamber on the downstream side thereof in communication with said valve, 9. by-pass valve controlling flow of fuel between said chambers arranged to by-pass fuel around said engine-driven pump when the pressures in said chambers attain predetermined relative-.values, a boost pump arranged to pressurize fuel into said intake chamber, and means for selectively operating said boost pump.

12. In a system for metering fuel to an engine wherein the flow of fuel through a conduit to the engine is regulated by a valve located in said conduit and controlled by an element rotating in synchronism with the engine and to which fuel is supplied under pressure by an enginedriven pump provided with a pumping element and a driving member therefor having a drive connection with both of said elements, means whereby should the pumping element of the engine-driven pump jam or seize the drive on said rotating element is maintained through said driving member, means defining an intake chamber on the upstream side of said engine-driven pump and a governor chamber on the downstream side thereof in communication with said valve, a by-pass valve between said chambers arranged to by-pass fuel around said engine-driven pump when the pressures in said chambers attain predetermined relative values, a boost pump arranged to pressurize fuel into said intake chamber, and means for indicating the pressure in said governor chamber.

13. In a system for metering fuel to an aircraft engine wherein the flow of fuel through a conduit to the engine is regulated by a valve located in said conduit and controlled by a governor rotating in synchronism with the engine and to which fuel is supplied under pressure by an engine-driven fuel pump provided with a pumping element and a driving member therefor having a driving connection with said governor and said element, means whereby should the pumping element of the engine-driven pump jam or seize the drive on said governor is maintained, means defining a low pressure intake chamber on the upstream side of said enginedriven fuel pump and a governor chamber on the downstream side thereof inccommunication with said valve, a by-pass valve controlling flow of fuel between said chambers-and arranged to open when the pressures in said chambers attain predetermined relative values, a'fuel tank. an electric boost pump submerged in said tank and arranged to deliver fuel under pressure to said intake chamber, a relief valve for said boost pump having a pressure-responsive control element vented to said fuel conduit upstream of said fuel valve and a spring augmenting the pressure of the fuel having a force substantially equal to the pressure drop across said fuel valve, an electric switch for selectively operating said boost pump, and means for indicating the pressure in said governor chamber.

JAY A. BOLT. FREDERICK P. JACKSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 473,949 McGowan May 3, 1892 1,564,215 Dillig Dec. 8, 1925 1,900,385 Kahr Mar. 7, 1933 1,906,334 Rathbun May 2, 1933 2,330,558 Curtis Sept. 28, 1943 2,409,931 Curtis Oct. 22, 1946 2,412,289 Pugh et al Dec. 10, 1946 Certificate of Correction Patent No. 2,531,664 November 28, 1950 JAY A. BOLT ET AL.

It is hereby certified that error the above numbered patent requiring Column 10, line 69, for valve read value; column 11, lines 31 and 60, after elements strike out the comma and insert instead a semlcolon; line 45, same column, for valves read values; columnlQ, line 11, after elements strike out the comma and msert instead a semlcolon; llnes 14: and 15, strike out 'd driving member;

the Words through sal and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

day of April, A. D. 1951.

Signed and sealed this 17th appears in the printed specification of correction as follows:

[SEAL] THOMAS F. MURPHY,

Assistant (lommissz'oner of Patents. 

